This invention relates generally to spectroradiometry and, more particularly, to techniques for selecting a desired sample of radiation for analysis in a spectroradiometer. In general, spectroradiometry is the spectral analysis of radiation received from a radiation source. Although spectroradiometry is used in a variety of applications, the present invention is principally concerned with spectroradiometry as applied in the spectral analysis of radiation emitted from a solar radiation simulator. Solar simulators are used to evaluate the performance of solar panels. Rather than exposing solar panels to sunlight, which may be impractical if the panels are to be deployed in space, a solar simulator is designed to generate a brief flash of radiation with a spectral content closely approximating that of the sun. Obviously, using a pulse of simulated radiation for this purpose requires less total energy that if a continuously operating simulator were used, and permits the use of components and conductors rated for much lower powers.
If a solar simulator is to be relied on in the testing of solar panels, the spectral content of the radiation generated by the solar simulator is of significant interest. In particular, what is of interest to solar panel designers is the spectral content of a solar simulator flash as recorded over a time interval that corresponds to the time interval of the flash used to evaluate solar panel performance. The spectral content of a flash of radiation from a solar simulator is known to vary with time as the energy of the flash builds to a plateau, and later decays. Unfortunately, a solar simulator typically provides no warning signal before it begins to produce a flash of output radiation, and yet spectral analysis of the flash must ideally be performed only over a narrow time interval at the same region of the flash of energy that is used in evaluating the solar panel or panels. Selection of this time interval using an electromechanical shutter to control the radiation has proved to be too slow. Typically, a simulated solar flash lasts for only approximately two milliseconds. The sample time of interest during the flash has to be determined with microsecond accuracy if useful spectral analysis is to be performed.
Accordingly, it would be desirable to be able to select with precision both a starting time and a time interval for analysis of the solar simulation flash, and to input the flash radiation to a spectroradiometry instrument only during this interval. The present invention satisfies this goal.